1. Field of the Invention
The present invention relates generally to cooling systems, and more particularly, to a self-contained, weather resistant, closed-loop cooling system which may be mounted on the exterior of an electrical cabinet for cooling electronic equipment within the cabinet.
2. Description of the Related Art
In a wide variety of indoor and outdoor, industrial and/or commercial applications, it is quite common for sensitive electronic equipment to be employed in environments where extreme temperature and/or humidity exist. These environments may also develop or create noxious and/or damaging fumes of a chemical nature which are emitted as by-products of the particular processes and/or machinery which the electronic equipment is designed to control.
As such, it is common to mount such sensitive electronic equipment within a sealed electric cabinet or enclosure in order to protect the sensitive electronic equipment from hostile elements outside the cabinet. The National Electrical Manufacturers Association (NEMA) has promulgated certain industry-wide standards for rating the ability of electrical cabinets (or other enclosures) to protect their interior from hostile elements outside the cabinet.
For instance, for an electrical cabinet or other enclosure to be rated NEMA 3R, it must be capable of providing a degree of outdoor protection against falling rain and sleet and be undamaged by the formation of ice on the cabinet. Similarly, to attain a rating of NEMA 4, an electrical cabinet must provide a degree of indoor or outdoor protection against splashing water, windblown dust and rain, and hose-directed water, and be undamaged by the formation of ice on the cabinet. A NEMA 4X rating contains all of the requirements of a NEMA 4 rating and further requires corrosion resistance.
Additionally, since electronic equipment frequently generate heat during their operation, temperature and humidity conditions within the cabinet housing the equipment must be closely controlled to further protect the electronic equipment from excessive heat and/or humidity within the cabinet. Therefore, heat generated by the sensitive electronic equipment within the cabinet must frequently be dissipated to the outside (ambient air side) of the cabinet as rapidly as it is produced.
Accordingly, to effectively cool the electronic equipment (and dehumidify the air within the cabinet depending upon the cooling system employed), while at the same time maintaining the protection of the electronic equipment from the hostile elements outside the cabinet, a closed-loop cooling system is commonly used which does not circulate air between the interior (warm air side) and exterior (ambient air side) of the cabinet. Instead, these closed-loop cooling systems provide two separate circulation systems. An internal circulation system cools and dehumidifies warm air within the electrical cabinet, totally isolating the sensitive electronics and other components from the outside environment. An external circulation system uses circulated ambient (outside) air to discharge the heat removed from the electronics within the enclosure.
These closed-loop cooling systems are typically single enclosures panel-mounted on the exterior of the electrical cabinet. One or more openings are generally cut into the electrical cabinet relative to the inlet and exhaust openings of the internal circulation system of the cooling system to facilitate air flow between the interior of the electrical cabinet and the cooling system. In this manner, the heat from the electronic equipment may be dissipated from the cabinet by an air conditioner with an air-cooled condenser or by a refrigerant-free heat exchanger.
In a closed-loop cooling system of the type comprising an air conditioner, such as that illustrated in FIG. 1, the heat is dissipated from the cabinet by means of a vapor compression refrigeration cycle in a hermetically-sealed refrigeration system [28] comprising a compressor [28'] and utilizing an air-cooled condenser coil [24]. The warm air [12] within the cabinet [10] is drawn into the internal circulation system in the front of the cooling system enclosure [20] by one or more fans or blowers and passes through an evaporator coil [22] within the cooling system where the warm air [12] is cooled, dehumidified and recirculated back into the cabinet [10] through the front of the cooling system enclosure [20] as illustrated by arrow [14] in FIG. 1.
The heat removed by the evaporator coil [22] is transferred by compressed refrigerant to a condenser coil [24] within the cooling system enclosure [20]. Ambient air [16] from outside the cabinet [10] is generally drawn into the top, rear, or sides of the cooling system enclosure [20] by one or more fans or blowers [26] and is passed through the condenser coil [24]. This ambient air flow absorbs the heat from the condenser coil [24] and is thereafter typically discharged to the ambient environment outside the cabinet [10] through the top, rear or sides of the cooling system enclosure [20] as illustrated by arrow [18] in FIG. 1.
A problem associated with these conventional closed-loop cooling systems stems from the fact that they require cutting one or more openings through the electrical cabinet relative the inlet and exhaust openings of the internal circulation system of the cooling system to facilitate air flow between the interior of the electrical cabinet and the cooling system enclosure. The ability to protect the interior of the electrical cabinet from the hostile environment outside the cabinet--and therefore the ability to maintain the desired NEMA rating--becomes increasingly difficult because the integrity of the electrical cabinet has now been compromised by these openings. In addition, the mounting of the cooling system enclosure--which is at least partially open to the outside environment to permit ambient cooling air to be supplied into and exhausted from the cooling system enclosure--will frequently lead to diminished protection of the interior of the electrical cabinet from the outside environment.